The present invention relates to compositions for conditioning the skin, nails, other tissue and/or body fluids of a human or other animal subject. More specifically, it relates to compositions which can be used to soften, smooth, lubricate and preserve the pliancy of human tissue, for reducing the brittleness of finger and toe nails, and as diluents for blood.
There presently exists a number of substances which are known to provide softening and other benefits to the skin when applied topically. The most popular of these is lanolin which is safe for topical applications and is used widely in cosmetic preparations.
To have a substantial effect, however, lanolin must be applied to the skin frequently and in large quantities. Even then, the softening effect on skin is less than has been obtained using lesser amounts of other skin softening substances. Compositions containing lanolin in sufficient quantity can leave the skin with a greasy feeling and may stain clothing if not thoroughly absorbed by the skin.
Due to the disadvantages of lanolin as a skin softener, substantial efforts have been made to find suitable alternative substances for skin conditioning. Unfortunately, most of the substances discovered have been synthetically derived and are not naturally occurring substances. Such substances are medically suspect and in some instances produce side-effects which make them unsuitable for use in cosmetics or other preparations for treating human tissue or body fluids.
One exception has been carbamide (urea) which is a naturally occurring substance in animals. Urea has been used with reasonable success for softening the skin and for treating skin diseases. Typically, the carbamide is applied in an aqueous solution or in the form of a cream. Such carbamide preparations have had only limited utility, however, because the carbamide tends to spontaneously decompose. As a result, preservatives for the carbamide must be added if such a skin treating composition is to have a reasonable shelf life.
The carbamide decomposition problem has been explored by a number of researchers. For example, Gunner P. E. Swanbeck has discovered various additives for stabilizing carbamide in a skin treating composition. In his U.S. Pat. No. 3,666,863, lactic acid is suggested as a preservative for skin treating compositions containing carbamide. And, in British Patent Specification No. 1,411,432, the same inventor describes a skin treating composition containing carbamide in combination with one or more salts selected from the group including sodium chloride, sodium thiosulfate and sodium dyhydrogen phosphate.
Even stabilized carbamide compositions of the type described in the Swanbeck references have their limitations. Most particularly, the effectiveness of urea as a skin treating agent is somewhat less than desired.
Another substance proposed for use in skin treating compositions is dimethyl sulfoxide (DMSO). As described in U.S. Pat. No. 3,549,770, DMSO has utility in relieving signs and symptoms of pain and tissue inflammation and for promoting tissue repair of a subject having a skin graft or suffering from burns or tissue damage. But, DMSO frequently causes adverse skin reactions so that DMSO has previously been considered unsuitable for use in cosmetics and other non-prescription preparations.
In general, it has been difficult to find substances which can be used to treat the tissues and body fluids of animal subjects without creating adverse side-effects. For example, after much research, dextran has become a widely accepted extender for blood plasma and is commonly used as a blood diluent. Despite the wide acceptance of dextran, this substance has a higher and more variable molecular weight than most normal blood constituents; and many subjects who receive the substancce react allergically. Other blood diluents have even greater drawbacks; so there is no universally accepted blood diluent or plasma expander.